Polishing media stabilizer

0001This application is a continuation of Ser. No. 09/258,036, filed Feb. 25, 1999, now U.S. Pat. No. 6,491,570.

TECHNICAL FIELD

0002The present invention relates to the field of polishing, and especially to chemical mechanical polishing. More specifically the present invention is directed to improvements in retention of the polishing surface and retention of polishing fluids during polishing.

BACKGROUND ART

0003Polishing a workpiece to produce a mirror-like, defect-free surface has applications in many fields of endeavor. Such polishing processes have become extremely important and widespread, for example, in the fabrication of semiconductor devices. The critical step of polishing a semiconductive wafer or substrate is required at a number of different stages along the varied processes employed to fabricate semiconductor devices.

0004Chemical mechanical polishing is rapidly becoming a technique of choice for polishing substrates, and particularly for use in the manufacture semiconductor devices on a wafer or substrate. The devices are connected by a process generally referred to as metalization, in which connecting lines of metal, often aluminum or copper, are applied by vacuum deposition or other suitable processes.

0005The performance level of semiconductor devices employing a conventional single metal layer connecting the devices is fast becoming unsuitable. Modern, high performance devices utilize multilevel metal interconnections. Multilevel connections may be constructed by depositing a dielectric or insulating layer over a first metal layer, etching via holes throughout the dielectric layer, and then depositing a second metal layer which fill the via holes to connect with the first metal layer. These devices offer higher device density and shortened interconnection lengths between the devices.

0006Since each of these metal and dielectric layers have an appreciable thickness, the wafer substrate is left with a non-planar topography as the various layers are patterned on top of one another. This type of non-planarity is often unacceptable in high density devices because the depth of field of the lithographic equipment that is used to print the smaller line width circuits on the wafer does not have a depth of focus sufficient to compensate for even small variations in wafer planarity.

0007In addition to the non-planarity caused by the fabricated device patterns, in-process wafer polishing, or planarization, must account for variations in overall wafer flatness as well. During the fabrication process, for example, the wafers may become bowed or warped.

0008In process polishing equipment, therefore, requires the specialized ability to achieve global, uniformly planar wafer surfaces in spite of these topographical wafer defects and variations. Chemical-mechanical polishing has gained wide acceptance as an effective means of achieving the global wafer surface planarity required by advanced devices employing multilayer metalization.

0009A typical chemical-mechanical polishing arrangement includes a wafer carrier having a generally circular pressure plate or carrier platen that supports a single substrate or wafer. A carrier film may be interposed between the carrier platen and the wafer. The wafer carrier is equipped with means to provide a downward force, urging the wafer against a polishing media (typically a circular pad), onto which is fed a polishing fluid. The polishing media is supported by a polishing platen. The polishing fluid may comprise a colloidal suspension of an abrasive and may also comprise a chemically reactive solution. A containment ring generally surrounds the wafer to prevent it from slipping off the carrier platen during polishing.

0010Typically, movement of the wafer relative to the pad, in the presence of the chemically reactive and/or abrasive polishing fluid and under pressure imparted by the wafer carrier, imparts a combination of chemical and mechanical forces to the wafer, the net effect of which is global planarization of the wafer surface. Generally, the polishing platen is rotatable as is the carrier platen. In a typical polishing apparatus, movement of the wafer relative to the pad is accomplished by rotating the polishing platen, the carrier platen, or both.

0011Rotating platen machines typically install a circular polishing pad and use it until the pad fails to obtain acceptable results because the pad becomes worn or becomes glazed with impacted polishing fluid and polishing particulate. At that time it is required to interrupt the polishing process and change the polishing pad. Other machines may use a rectangular pad or a continuous supply of polishing pad material that may be incrementally advanced over the polishing platen, to ensure that the polishing pad is never too worn to be effective.

0012Regardless of the configuration of the polishing pad, a common problem that occurs when the pad is not fixed to the polishing platen with an adhesive or other fixing means, is that the polishing pad migrates from its position when polishing forces are applied to it by the wafer carrier through the wafer. This migration results because the frictional forces between the wafer and the polishing pad, together with any chemical polishing media that might be employed, are greater that the frictional forces that exist between the polishing pad and the polishing platen. Such migration reduces the productivity and that accuracy of the polishing process requiring at least a reduction in the polishing pressure used in the process, thereby increasing the polishing time. Worse, the polishing pad may buckle during migration, resulting in nonplanar polishing results or total failure of the process (e.g. breakage of the substrate). These problems are not solely limited to chemical mechanical polishing but may also occur in purely mechanical polishing processes.

0013A problem that occurs particularly in chemical mechanical polishing machines is depletion of the chemical fluid or slurry between the substrate to be polished, and the polishing pad after a certain amount of polishing motion has occurred. Because of the relatively smooth and planar surfaces that comprise the polishing pad/platen and the substrate surface being polished, the polishing action tends to “sweep out” the chemical fluid/slurry and a vacuum or suction builds up between the substrate surface being polished and the polishing pad. Thus, this problem gets progressively worse with polishing time. Ironically, the problem also magnifies as the surface of the substrate becomes more planar and smooth, although the problem reduces the polishing efficiency and performance of the process.

0014It would be desirable to have an apparatus with the capability to prevent migration of the polishing pad, while at the same time allowing easy and quick replacement either continuously or intermittently. It would also be desirable to prevent the elimination of the chemical polishing agent, e.g., the phenomena known as “slurry starvation” between the substrate surface to be polished and the polishing pad.

DISCLOSURE OF THE INVENTION

0015The present invention addresses the above problems, among other advantages to be further developed in the following detailed description. An apparatus for stabilizing a polishing surface includes a substantially planar inflexible support base, a flexible polishing pad overlying the support base, and a vacuum port in the support base and underlying the polishing pad. When vacuum is applied through the vacuum port, the polishing pad is pulled against the support base to maintain the polishing pad in a predetermined polishing position. A seal is preferably provided to form a perimeter around the vacuum port on the support base. An airtight seal is formed between the support base and the polishing pad along the seal upon application of the vacuum.

0016Another embodiment employs a plurality of vacuum ports to more evenly distribute the application of vacuum. For example, the plurality of vacuum ports may lie around a perimeter of the support base. Alternatively, the plurality of vacuum ports may be substantially equally distributed over the support base. The plurality of vacuum ports may include a group of relatively larger vacuum ports around a perimeter of the support base and a group of relatively smaller vacuum ports substantially equally distributed over an area of the support base within the perimeter.

0017The present invention further includes the placement of an additional layer between the polishing pad or media and the support base. The additional layer is provided so that, when the polishing pad is drawn against the support base by application of vacuum, nonplanarities are formed in the polishing pad. These nonplanarities help retain polishing fluid in the polishing area of the polishing pad during polishing of a substrate.

0018The additional layer is preferably a resilient pad. The additional layer is perforated so that portions of the polishing pad are partially drawn into the perforations upon the application of vacuum. Preferably, the perforations have a diameter or size in the range of about 0.06 to about 0.25 inches.

0019As a means for fixing a polishing pad during polishing, a polishing apparatus according to the present invention includes a substantially planar inflexible support base, a flexible polishing pad overlying the support base, and means for drawing the polishing pad against the support base to maintain the polishing pad in a predetermined polishing position. Preferably, the drawing means comprise a vacuum source connected to at least one vacuum port in the support base, but other arrangements such as a source to draw the polishing pad to the head may be alternatively used as discussed below. Further, a substrate carrier is movably mounted with respect to the polishing pad and the support base.

0020A pad may be interposed between the flexible polishing pad and the support base. Preferably, the pad is perforated or porous. More preferably, the pad is a perforated resilient pad.

0021Also disclosed is a method of stabilizing a polishing media during polishing of a substrate against the polishing media. The method includes providing a polishing media over a substantially inflexible support surface, and applying a vacuum between the support surface and the polishing media to draw the polishing media toward the support surface. The vacuum is applied with a force of about 0.2 to 3.0 psi, preferably about 1.2 psi.

0022The method preferably further includes polishing a substrate against the polishing media while maintaining the vacuum to deter movement of the polishing media with respect to the support surface. Still further, the method may include removing the substrate from contact with the polishing media, discontinuing application of the vacuum and removal of the polishing media for cleaning, conditioning or replacement.

0023The method may include replacing the same polishing media after cleaning and/or conditioning it. After replacing the same polishing media, the vacuum is reapplied between the support surface and the polishing media to draw the polishing media toward the support surface. Alternatively, another polishing media may be positioned on the support surface to replace the original polishing media. Once the new polishing media is positioned, the vacuum is then reapplied between it and the support surface to draw it toward the support surface.

0024Optionally, a porous layer may be provided between the polishing media and the substantially inflexible support surface prior to applying the vacuum. Then, upon application of the vacuum, portions of the polishing media are partially drawn into porosities of the porous layer to form dimples on a polishing surface of the polishing media.

0025An apparatus for stabilizing a polishing surface is disclosed to include a substantially inflexible support base; a flexible polishing pad overlying at least a portion of the support base; and a carrier for applying a substrate against the polishing pad to polish the substrate. Means for maintaining the flexible polishing pad substantially wrinkle free with respect to the substrate may include a vacuum port in the support base and underlying the polishing pad, or a mechanism for drawing the flexible polishing pad against the carrier and the substrate, for example.

0026When at least one vacuum port is provided in the support base, application of vacuum therethrough pulls the polishing pad against the support base to maintain the polishing pad in a predetermined polishing position. When the means for maintaining includes a mechanism for drawing the flexible polishing pad against the carrier and the substrate, at least one vacuum port may be formed in the carrier. A vacuum source is provided for applying a vacuum between the carrier and the polishing pad via the at least one vacuum port, thereby maintaining the polishing pad substantially wrinkle-free, at least in the portion underlying the carrier and substrate at any given time.

BRIEF DESCRIPTION OF THE DRAWINGS

0027<figref idref="DRAWINGS">FIG. 1</figref> is a partial cross-sectional view of an example of a polishing apparatus and the basic components thereof.

0028<figref idref="DRAWINGS">FIG. 2</figref> is a top view of a first example of the present invention which employs a circular support base.

0029<figref idref="DRAWINGS">FIG. 3</figref> is a schematic view of a polishing apparatus in which a polishing media magazine is employed.

0030<figref idref="DRAWINGS">FIG. 4</figref> is a partial isometric view of a polishing system according to another embodiment of the present invention which employs a polishing media magazine.

0031<figref idref="DRAWINGS">FIG. 5A</figref> is a sectional view of the apparatus shown in FIG. <b>4</b> and taken along line <b>5</b>—<b>5</b> with the vacuum applied.

0032<figref idref="DRAWINGS">FIG. 5B</figref> is a sectional view of the apparatus shown in FIG. <b>4</b> and taken along line <b>5</b>—<b>5</b> when the vacuum is not applied.

0033<figref idref="DRAWINGS">FIG. 6</figref> is a partial view of a variation of the system shown in FIG. <b>4</b>.

0034<figref idref="DRAWINGS">FIG. 7</figref> is a partial view of a polishing system having another variation in the arrangement for applying vacuum to the interface between the support member and the polishing media.

0035<figref idref="DRAWINGS">FIG. 8</figref> is a partial view of a polishing system having yet another variation in the arrangement for applying vacuum to the interface between the support member and the polishing media.

0036<figref idref="DRAWINGS">FIG. 9</figref> is a partial view of a polishing system having a variation of <figref idref="DRAWINGS">FIG. 8</figref>, in the arrangement for applying vacuum to the interface between the support member and the polishing media.

0037<figref idref="DRAWINGS">FIG. 10</figref> is a cutaway view of an arrangement of a polishing apparatus which is also adapted toward addressing the problem of depletion of the polishing fluid during polishing.

0038<figref idref="DRAWINGS">FIG. 11</figref> is a partial sectional view which illustrates the formation of dimples in the polishing surface of the polishing media.

0039<figref idref="DRAWINGS">FIG. 12</figref> is a partial perspective view of a polishing system according to another embodiment of the present invention.

0040<figref idref="DRAWINGS">FIG. 13</figref> is a view of the support member used in the embodiment of FIG. <b>12</b>.

0041<figref idref="DRAWINGS">FIG. 14</figref> is a sectional view of an apparatus employing the principles of the system shown in FIG. <b>12</b>.

0042<figref idref="DRAWINGS">FIG. 15</figref> is a sectional view of another embodiment of a substrate carrier for use in employing the principles of the system shown in FIG. <b>12</b>.

BEST MODE FOR CARRYING OUT THE INVENTION

0043Referring to the drawings in detail wherein like numerals indicate like elements, the present invention generally involves improvements to the polishing pad of a polishing apparatus. To better understand the invention outlined below, it is useful to understand the basic components of the polishing apparatus.

0044Referring to <figref idref="DRAWINGS">FIG. 1</figref>, a substrate carrier <b>120</b> is generally positioned over a support base <b>250</b> which typically supports a polishing pad or strip <b>220</b>. Substrate carrier <b>120</b> is generally capable of supporting a wafer or substrate while supplying the required force to facilitate polishing. Substrate carrier <b>120</b> may have some ability to self align the substrate <b>260</b> to the plane of support base <b>250</b>. Optionally, a resilient pad <b>240</b> may be interposed between the polishing pad or polishing media <b>220</b> and the support base <b>250</b> for improved polishing in certain circumstances. The substrate carrier <b>120</b> may have a spindle <b>270</b> to which the required downward force and rotational forces are applied. As mentioned above, the substrate carrier <b>120</b> is preferably capable of self alignment so as to align the substrate <b>260</b> to the polishing media <b>220</b>. Although there are many other possibilities, the substrate carrier <b>120</b> may allow for the rotation of the lower member <b>290</b> relative to the upper member <b>280</b> about a bearing means <b>285</b>. Polishing fluid may be applied in metered fashion to the polishing media <b>220</b> by way of polishing fluid nozzle <b>230</b>.

0045Various relative motions may be applied between the substrate <b>260</b> and the polishing media <b>220</b> to effectuate a polishing action. For example, one type of relative motion is achieved by maintaining the support base <b>250</b> non-movable with respect to ground and controllably moving the substrate carrier <b>120</b>. The substrate carrier may be controlled by a motion controller (not shown) which is capable of controlled, or programmed movement along directions which are parallel to the plane of the support surface <b>250</b>. Alternatively or additionally, the substrate carrier may be rotated about the axis defined by the spindle <b>270</b>. Movement in each of the directions may be, and typically is, programmed to occur simultaneously.

0046<figref idref="DRAWINGS">FIG. 2</figref> shows a top view of a first example of the present invention which employs a circular support base <b>150</b>. A flexible polishing pad <b>170</b> overlies the circular support base <b>150</b>. An optional resilient pad (not shown), similar to the resilient pad <b>240</b> discussed above, may be employed between the flexible polishing pad <b>170</b> and the support base <b>150</b>. The circular support base <b>150</b> may be rotatable so as to effectuate polishing forces against a substrate <b>260</b> when the substrate is held against the polishing pad <b>170</b> by means of a substrate carrier <b>180</b>. Alternatively, the support base <b>150</b> may be held stationary while the carrier <b>180</b> is moved to effectuate the polishing action between the substrate <b>260</b> and the polishing pad <b>170</b>. The substrate carrier <b>180</b> is preferably programmable so as to move linearly, rotationally, or according to a combination of both type movements with respect to the support base <b>150</b> and polishing pad <b>170</b>.

0047Accordingly, there is effectively no limit to the patterns of polishing which can be accomplished by the carrier <b>180</b> with respect to the support base <b>150</b> and polishing pad <b>170</b>. Another alternative operation of the apparatus shown in <figref idref="DRAWINGS">FIG. 1</figref> is the simultaneous movement of both the carrier <b>180</b> and the support base <b>150</b> with respect to one another. This would generally involve the rotation of the support base <b>150</b> while the carrier <b>180</b> is also moved rotationally, linearly, or a combination of both types of movement.

0048Many conventional polishing apparatuses that have a rotating support base also fix the polishing pad to the support base with an adhesive. Such an arrangement is unwieldy when it comes time to change the polishing pad due to wear or caking. Removal of the polishing pad is not easily accomplished and portions of the pad and or adhesive may remain and require additional attention to ensure that the support base remains very planar when the new polishing pad is attached. Thus, this can be a very tedious and time consuming process that hinders production by causing down time.

0049However, as mentioned above, a common problem that occurs when the pad is not fixed to the polishing platen with an adhesive or other fixing means, is that the polishing pad migrates from its position when polishing forces are applied to it by the substrate carrier through the substrate. The migration results because the frictional forces between the substrate and the polishing pad, together with any chemical polishing media that might be employed, are greater that the frictional forces that exist between the polishing pad and the support base (polishing platen).

0050The arrangement in <figref idref="DRAWINGS">FIG. 2</figref> overcomes the problems incurred with an adhesively applied polishing pad, as well as the problems mentioned with regard to a pad that is not adhesively fixed. A vacuum port <b>190</b> is formed in the support base <b>150</b> and connected to a vacuum source (not shown in FIG. <b>2</b>). For support bases <b>150</b> that rotate, the vacuum source may interface with the vacuum port via slip rings or other equivalent arrangements known in the art. A sealing barrier <b>195</b>, preferably a sealing ring such as a strip of IC1000 material (supplied by RODEL), an O-ring or some other material forming an effective vacuum seal, surrounds the vacuum port and follows a contour that is just inside the perimeter of the polishing pad <b>170</b>. Thus, after positioning the polishing pad <b>170</b> on the support base <b>150</b>, a vacuum can be drawn through the vacuum port <b>190</b> which forms an effective air seal along the sealing barrier <b>195</b>. Once the air seal is formed, essentially any air existing between the polishing pad <b>170</b> and support base <b>150</b> is removed by the vacuum source thereby effectively fixing the polishing pad <b>170</b> to the support base <b>150</b>.

0051<figref idref="DRAWINGS">FIG. 3</figref> shows an embodiment of a polishing apparatus in which it is impractical to adhesively fix a polishing pad to a support base and in which the present invention is all the more important. In this embodiment, a polishing media magazine <b>350</b> is employed rather than an individual polishing pad <b>170</b>. The polishing media magazine <b>350</b> is shown with an associated substrate carrier <b>354</b> that may be controlled in any of the movements described above with respect to the carrier <b>180</b> in FIG. <b>2</b>. An optional polishing fluid delivery nozzle <b>352</b> may supply polishing fluid to the polishing media <b>310</b>. The polishing fluid delivery nozzle <b>352</b> may be attached to and move with substrate carrier <b>354</b> or may be separately located or both arrangements may be used. The substrate carrier is shown for illustration purposes only, and may be substituted by other arrangements such as a substrate carrier driven by linear motors for example.

0052The polishing media magazine <b>350</b> preferably uses a polishing media <b>310</b> that is supplied in the form of a long media roll. The polishing media <b>310</b> preferably comprises a thin polymeric film substrate having either a polishing pad or a fixed abrasive covering over at least a portion of the width thereof. The film may be on the order of 0.001 to 0.020 inches thick, preferably around 0.005 to 0.007 inches thick. The polishing media <b>310</b> should be substantially impermeable to the polishing fluid. Preferably the material is made of Mylar film or polyethylene glycol terephthalate. New polishing media <b>310</b> is preferably automatically supplied by the polishing media magazine <b>350</b> so that user intervention is not required until the entire roll has been consumed.

0053The polishing media <b>310</b> may take a variety of paths through the polishing media magazine depending on the desired configuration and features desired to be interposed within the polishing media path. The paths are described in detail in copending U.S. application Ser. No. 08/833,278 filed on Apr. 4, 1997 and entitled “Polishing Media Magazine For Improved Polishing”, which is hereby incorporated by reference herein in its entirety. In <figref idref="DRAWINGS">FIG. 3</figref> the media is roll fed from supply roll <b>300</b> under a first rolling turnbar <b>320</b> and across top surface <b>356</b> of platen support <b>355</b>. Polishing media <b>310</b> exits the top surface <b>356</b> over a second rolling turnbar <b>325</b>, passes around conditioning system <b>305</b>, around third turnbar <b>330</b> and finally onto take-up roll <b>340</b>. The third rolling turnbar <b>330</b> is preferably located at a vertical elevation which is lower that the take-up roll <b>340</b>. With this configuration, the resulting angle <b>359</b> tends to concentrate the polishing fluid at third rolling turnbar <b>330</b> for consistent release from the polishing media <b>310</b> into waste tank <b>358</b> as shown.

0054A tensioned portion of the polishing media may be positioned accurately with respect to other features of the polishing media magazine by supporting the tensioned portion with precisely placed turnbar elements. These turnbar elements are typically cylindrically ground elongated cylinders or rods supported at each end by bearings. While these rolling turnbars are typically used to reduce overall friction and wear in the system, other non-rotating elements, such as a porous web roll or porous flotation roll, for example, may be employed to yield the desired polishing media path. Such an example provides a totally now-contact method of transporting the media.

0055Whatever the elements that are used to form the polishing media path, a tensioned portion is still not entirely resistant to the migration and buckling problems, discussed earlier, that can occur during polishing. To further fix the tensioned portion in position during polishing, polishing apparatuses that employ a polishing media magazine may also be employed with a vacuum fixation system according to the present invention. The present system can be applied to those apparatuses regardless of whether they use a slurry or slurry-less type of polishing media.

0056The vacuum system draws a vacuum between the tensioned portion of the polishing media and the polishing support surface, to increase the force with which the tension portion is held in its position. As a result, the attraction forces between the polishing media and support surface are greater than the frictional forces between the between the substrate and the polishing media, together with any chemical polishing media that might be employed, and no migration or buckling of the polishing media occurs. This type of solution is not solely limited to chemical mechanical polishing, but may be applied to mechanical polishing apparatuses as well. Additionally, the force supplied by the vacuum system may be sufficient to prevent migration or buckling without the need to tension the polishing media.

0057In the example shown in <figref idref="DRAWINGS">FIG. 3</figref>, a vacuum source <b>192</b> is connected to a vacuum port <b>190</b> that passes through the support <b>355</b>. Although not shown, a sealing barrier <b>195</b> is positioned around the vacuum port <b>190</b>, similar to that described with regard to FIG. <b>2</b> and lying just inside the perimeter of the tensioned portion of the media <b>310</b>. the vacuum source is preferably a high volume, low pressure blower (for example, supplied by GAST, FUJI or AMETEC) that generates about 0.2 to 3.0 psi vacuum at the polishing media. A preferred vacuum to be applied is about 1.2 psi. A venturi pump may be used to generate about 3-4 psi vacuum to the media when the media used is thicker than the averages discussed above.

0058A typical operation of the apparatus in <figref idref="DRAWINGS">FIG. 3</figref> would involve indexing of the media <b>310</b> to position a predetermined portion of the media above the surface <b>356</b>, tensioning the predetermined portion of the media <b>310</b> above the surface <b>356</b>, and then applying vacuum via the vacuum source <b>192</b>. Upon forming a seal between the media <b>310</b> and the surface <b>356</b> via the sealing barrier, the vacuum would then evacuate all air existing between the media <b>310</b> and surface <b>356</b> at which time the media would become essentially fixed to the surface <b>356</b>. Polishing operations can next be commenced. The vacuum is preferably maintained until a movement of the media is desired, whether for conditioning or cleaning purposes or to advance to a new portion of the media to be used for polishing.

0059<figref idref="DRAWINGS">FIG. 4</figref> is a partial view of a polishing system according to another embodiment of the present invention. The polishing media <b>310</b> passes over roller <b>420</b>, but this is of no consequence to the present invention. In this embodiment the longitudinal edges of the support surface underlying the polishing media <b>310</b> are raised in height with respect to the remainder of the support surface by movable edge elements <b>465</b>. Although not stated above, the longitudinal edges of the surface <b>356</b> may optionally be raised with respect to the remainder of the surface <b>356</b>, however the edges are integral with the remainder of surface <b>356</b>. The media <b>310</b> need only have a working area for polishing as wide as the planar section between the raised edge sections. The area outside of the working width need not be coated, thus saving material expense.

0060The raised edge portions aid in creating raised edges of the polishing media <b>310</b>. For embodiments that use a slurry in the polishing process, the raised edges aid in maintaining the slurry in the polishing area and in channeling the slurry to an appropriate receptacle for either recycling or disposal. More important to the present invention, the raised edges also urge the media <b>310</b> against the sealing barrier to make sure that a vacuum can be reliably drawn upon application of vacuum to the system through the vacuum source <b>192</b>.

0061The movable edge elements <b>465</b> are particularly effective in maintaining close positioning of the sealing barrier <b>495</b> with the polishing media <b>310</b> as shown in <figref idref="DRAWINGS">FIGS. 5A-5B</figref>. The edge elements <b>465</b> are vertically biased upwardly with respect to the support member <b>455</b> by biasing elements <b>468</b>, as shown in FIG. <b>5</b>B. The biasing elements <b>468</b> are preferably springs, most preferably a type of coil springs, but other springs with equivalent biasing characteristics may be readily substituted, as may other resilient biasing mechanisms such as o-rings, bladders, pneumatic or hydraulic devices, etc.

0062Upon application of vacuum through the vacuum port <b>190</b>, a seal is formed between the media <b>310</b> and sealing barrier <b>495</b>. The media is then drawn flat against the support surface <b>465</b> and secured there by the vacuum pressure as shown in FIG. <b>5</b>A. Note that the vacuum force is enough to overcome the biasing force of the biasing elements <b>468</b>, which are compressed and the edge elements <b>465</b> are depressed into their lowermost vertical position as they bottom out when the biasing elements <b>468</b> become fully depressed, as shown in FIG. <b>5</b>A. In their lowermost positions, the edge elements <b>465</b> align the polishing media <b>310</b> to ensure a smooth and flat interface over the entirety of the planar polishing surface <b>465</b> that the edge elements <b>465</b> border.

0063Upon release of the vacuum, the biasing force of the biasing elements becomes greater than the minimized downward force of the media <b>310</b>. As a result, the edge elements <b>465</b> are biased into their uppermost positions as shown in FIG. <b>5</b>B. By assuming the uppermost positions, the edge elements ensure that the sealing barrier along the longitudinal edges remains in contact with the media <b>310</b> when the vacuum is lacking, as also shown in FIG. <b>5</b>B. This greatly improves the reliability of the system in ensuring that a vacuum can be drawn once again at the desired time.

0064The partial view of a polishing system <b>550</b> shown in <figref idref="DRAWINGS">FIG. 6</figref> shows a variation in the arrangement for applying vacuum to the interface between the support surface <b>456</b> of the support member <b>455</b> and the polishing media <b>310</b>. In this arrangement, a plurality of vacuum ports <b>290</b> are spaced along the surface <b>456</b> just inside the perimeter defined by the sealing barrier <b>495</b>. In the example shown, the vacuum ports <b>290</b> are evenly distributed and are of equal size. However, the invention is not to be so limited. The distribution of vacuum ports may be more concentrated, for example along the width edges to compensate for the lack of elevated edges in these areas. Alternatively, or in addition thereto, the vacuum ports may be of unequal size in different locations to tailor the application of vacuum as preferred. Also, many small vacuum ports could be distributed throughout the surface <b>456</b> to accomplish a secondary objective of assisting in the prevention of slurry/liquid starvation, which will be discussed in more detail below.

0065<figref idref="DRAWINGS">FIG. 7</figref> shows a partial view of a polishing system <b>650</b> having another variation in the arrangement for applying vacuum to the interface between the support surface <b>556</b> of the support member <b>555</b> and the polishing media <b>310</b>. In this arrangement, a plurality of very small vacuum ports <b>390</b> up to a quarter of an inch (0.25″), preferably up to an eighth of an inch (0.125″) are distributed over the entire working area (i.e., area underlying the tensioned portion of the polishing media and lying within the boundary of the sealing barrier <b>495</b>) of the surface <b>556</b>. In the example shown, the vacuum ports <b>290</b> are substantially evenly distributed and are of substantially equal size. However, the invention is not to be so limited. The distribution of vacuum ports may be more concentrated, for example near the perimeter of the surface adjacent the sealing barrier <b>495</b>. Alternatively, or in addition thereto, the vacuum ports may be of unequal size in different locations to tailor the application of vacuum as preferred. For example, the vacuum ports may be larger along the inside of the perimeter of the sealing barrier <b>495</b>, as compared to the vacuum ports further inside the sealing barrier (closer to the center of the surface <b>556</b>).

0066All of the foregoing embodiments may be constructed so as to have elevated, integral longitudinal edges, movable elevated edge elements, or edges which are coplanar with the remainder of the support surface.

0067<figref idref="DRAWINGS">FIG. 8</figref> shows a partial view of a polishing system <b>475</b> having another variation in the arrangement for applying vacuum to the interface between the support surface <b>478</b> of the support member <b>476</b> and the polishing media <b>310</b>. In this arrangement, a groove or channel <b>477</b> is formed into the support surface <b>478</b> generally around the periphery thereof, but inside the bounds of the sealing barrier <b>495</b>. A vacuum source (not shown, but like described with regard to <figref idref="DRAWINGS">FIG. 3</figref>) is connected to the channel <b>477</b> via a vacuum port <b>479</b> that passes through the support <b>476</b>.

0068Upon application of the vacuum, existing air, between the polishing media <b>310</b> and portion of the polishing surface <b>478</b> lying inside the sealing barrier <b>495</b>, is evacuated through the channel <b>477</b> and port <b>479</b> so as to draw the polishing media <b>310</b> against the polishing surface <b>478</b> to securely hold the polishing media in position during the polishing process. In the example shown, the channel <b>477</b> is substantially uniformly dimensioned around the entire periphery thereof. However, the invention is not to be so limited, as the channel can be formed to be wider or deeper in select areas such as the corners or ends of the rectangular pattern shown. Also, the channel can be formed in other configurations, such as oval, hourglass, etc.

0069<figref idref="DRAWINGS">FIG. 9</figref> shows another variation that may be practiced using vacuum channels. In this embodiment, an additional channel <b>487</b> is formed interiorly of the perimeter established by the channel <b>477</b>. The two channels <b>477</b> and <b>487</b> are connected by a connecting port <b>488</b> which lies beneath the polishing surface <b>489</b>. Alternatively, a channel could be formed in the polishing surface <b>489</b> to connect the channels <b>477</b> and <b>487</b>, but a port <b>488</b> is preferred. Since the channel <b>487</b> will generally lie more in the path of polishing, it is preferable, but not necessary, to form the channel <b>487</b> to be narrower than channel <b>477</b>, so as not to significantly disrupt the planarity of the polishing surface. A port <b>491</b> connects the channels <b>477</b>,<b>487</b> and port <b>488</b> to a vacuum source (not shown).

0070All of the foregoing embodiments may be constructed so as to have elevated, integral longitudinal edges, movable elevated edge elements, or edges which are coplanar with the remainder of the support surface.

0071<figref idref="DRAWINGS">FIG. 10</figref> is a cutaway view of an arrangement of a polishing apparatus which is also adapted toward addressing the problem of depletion of the chemical fluid or slurry or other fluid which is used between the substrate to be polished and the polishing pad during polishing. As referred to above, after a certain amount of polishing motion has occurred, this fluid tends to become more and more depleted until there is virtually no fluid between the substrate and polishing pad. Because of the relatively smooth and planar surfaces that comprise the polishing pad/platen and the substrate surface being polished, the polishing action tends to “sweep out” the chemical fluid/slurry and a vacuum or suction builds up between the substrate surface being polished and the polishing pad.

0072The polishing apparatus <b>750</b> includes a porous, resilient layer <b>710</b> between the polishing media <b>310</b> and the support surface <b>556</b>. When vacuum is applied via the vacuum port <b>190</b>, the polishing media <b>310</b> is forced toward the support surface <b>556</b> with a force sufficient to at least partially compress the resilient layer <b>710</b>. The thin polishing media is further drawn against the resilient layer <b>710</b> and partially into the porosities <b>720</b> within the resilient layer <b>710</b> as air is depleted from the porosities. The result is that a plurality of concavities or “dimples” are formed in the polishing surface of the polishing media <b>310</b>. A partial sectional view of the relationship between the support <b>555</b>, resilient layer <b>710</b>, polishing media <b>310</b> and substrate <b>260</b> is diagrammed in FIG. <b>11</b>.

0073Concavities <b>810</b> in the polishing media <b>310</b> are formed over the porosities <b>720</b> of the resilient layer <b>710</b> when the vacuum is applied as described above. the concavities act as capacitances for slurry, KOH, water, or whatever liquid medium <b>840</b> is used during the polishing process. Thus, even when a very planar substrate <b>260</b> passes over the polishing media <b>310</b>, not all of the fluid <b>840</b> is swept out of the polishing area. Rather, pockets of fluid/polishing medium remain in the dimples <b>810</b> to help prevent slipping/sticking (e.g., “stiction”) problems that are often observed as a result of slurry/fluid starvation beneath the substrate to be polished.

0074A preferred resilient layer is the IC1000 pad supplied by RODEL, although other available equivalent porous and resilient materials may be substituted. Alternatively, relatively non-resilient layers having a porosity similar to IC1000 may be successfully used for dimple formation in the polishing media <b>310</b>. Still further, dimples may be formed in the polishing media <b>310</b> if the layer between the polishing media <b>310</b> and support surface <b>555</b> is left out altogether, when the support surface <b>556</b> is provided with vacuum ports <b>390</b>, similar to those shown in <figref idref="DRAWINGS">FIG. 7</figref>, that are close to the pore size of IC1000.

0075<figref idref="DRAWINGS">FIG. 12</figref> is a partial view of a polishing system according to another embodiment of the present invention. The polishing media <b>310</b> passes over rollers <b>420</b> and <b>325</b> as in previous embodiments, but, as in the previous embodiments, this is of no consequence to the present invention, as the present invention may be practiced with other media arrangements, e.g., a single flexible sheet of polishing media. In this embodiment the support surface <b>856</b> of the support member <b>855</b> is hollowed out or at least recessed in the central portion <b>857</b> thereof (see also FIG. <b>13</b>).

0076The edge surfaces <b>858</b> support the polishing media <b>310</b> and the polishing media is preferably tensioned over the surface <b>855</b> and clamped to the edge surfaces <b>858</b> by clamps <b>870</b> with or without the application of vacuum to the periphery of the polishing media, preferably with. The media is preferably tensioned to at least 2 lbf per inch of media width. Preferably the clamping is performed near the four corners of the table using four clamps <b>870</b> as shown, but more or fewer clamps may be used. Alternatively, the media may be clamped along the entire edge thereof along both side using long clamps the surfaces of which are extended by an underlying foam or other soft tapering substance.

0077The substrate carrier <b>860</b> is provided with at least one vacuum port <b>865</b> preferably in an area surrounded by the containment ring <b>868</b> or other structure outlying the substrate <b>260</b>. The vacuum port <b>865</b> is connected to a vacuum source <b>880</b> via a vacuum tube <b>890</b>. As in the previous embodiments, this embodiment is not limited to the use of a single vacuum port, but alternative arrangements may include multiple vacuum ports of equal or unequal size, variously spaced around the perimeter of the ring area. Preferably, when a multitude of vacuum ports are employed, the vacuum ports are equally spaced about the ring area, but this is also not absolutely necessary.

0078At least one sealing barrier <b>866</b> is provided around the perimeter of the substrate carrier <b>860</b>, preferably very close to the edge of the carrier <b>860</b> and necessarily surrounding the vacuum port(s) <b>865</b>. Preferably, the surface of the containment ring <b>868</b> that contacts the polishing media <b>310</b> functions as the sealing barrier <b>866</b>. Optionally, a dedicated sealing barrier may be positioned either on the containment ring contacting surface, or adjacent the inside circumference of the containment ring <b>868</b>. Upon application of vacuum through the vacuum port <b>865</b>, a seal is formed between the media <b>310</b> and sealing barrier <b>866</b>. The media is then drawn flat against the substrate <b>260</b> and bottom surface of the substrate carrier <b>860</b> and secured there by the vacuum pressure drawn through vacuum port <b>865</b>.

0079Polishing of the substrate may next be commenced. Pressure applied by the substrate carrier <b>860</b> against the substrate <b>260</b> works against the vacuum force that draws the media <b>310</b> against the surface of the substrate <b>260</b> to be polished, thereby providing the working pressure needed to polish the substrate (i.e., the “P” variable in Preston's equation). One advantage of this arrangement is that an absolutely flat, planar polishing or support surface is not required. Additionally, a much lighter weight support member <b>855</b> is possible due to the recessed or hollow central portion that does not need to be capable of providing a support against which the polishing will take place.

0080Upon release of the vacuum, the biasing force of the tensioned media <b>310</b> becomes greater than any attractive forces that might possibly remain between the media <b>310</b> and the substrate <b>260</b> and carrier <b>860</b>. As a result, the media <b>310</b> withdraws from contact with the substrate <b>260</b> and substrate carrier <b>860</b> and resumes a substantially planar configuration which is substantially coplanar with support <b>855</b>. An optional feature may be provided on carrier <b>860</b> to provide a positive force such as positive fluid pressure (preferably air) against the media <b>310</b> after release of vacuum pressure to assist in separating the media <b>310</b> from the substrate <b>260</b> and carrier <b>860</b>.

0081The carrier <b>860</b> is then elevated from the media <b>310</b> to enable easy removal of the substrate <b>260</b> for inspection and/or replacement. Once a substrate is repositioned between the media <b>310</b> and carrier <b>860</b>, the carrier <b>860</b> is repositioned near or against the media <b>310</b>. Reapplication of vacuum produces a seal as described above, at which time polishing is recommenced.

0082<figref idref="DRAWINGS">FIG. 14</figref> is a sectional view of a system using the vacuum techniques described above with respect to <figref idref="DRAWINGS">FIGS. 12 and 13</figref>. Also shown is an embodiment of a substrate carrier <b>860</b>. The plate <b>955</b> of the substrate carrier <b>860</b> forms an upper reference plane from which the force application means <b>960</b> apply the load to the substrate <b>260</b>. In this example, the force application means include three concentric rings <b>961</b>, <b>962</b> and <b>963</b> which are configured to emit controlled flows of gas and/or liquid. Preferably, the application means <b>961</b>, <b>962</b> and <b>963</b> emit air to form a pressurized air layer <b>970</b> between the plate <b>955</b> and the substrate <b>260</b>. However, other gases, water, a mixture of water and air and/or other gases, or vacuum may also be employed in forming a bearing or fixation layer <b>970</b> between plate <b>955</b> and substrate <b>260</b>. Of course, this type of carrier is not limited to the use of three rings, but may use four rings or more, or even one or two rings.

0083In the embodiment shown, pressure lines <b>964</b>, <b>965</b> and <b>966</b> connect the rings <b>961</b>, <b>962</b> and <b>963</b>, respectively to a source of pressurized air (not shown). Throttle valves <b>967</b> are provided on each of the lines to enable an operator to independently regulate the flow through each of the rings <b>961</b>, <b>962</b> and <b>963</b> while using a single pressure input line <b>968</b>. A more detailed and complete description of such a carrier is set forth in a co-pending application entitled “Padless Substrate Carrier” filed on even date herewith and bearing Attorney's Docket No. 36172-20017.00. The aforementioned “Padless Substrate Carrier” application is hereby incorporated by reference thereto in its entirety.

0084Optionally, slurry lines <b>972</b> may pass through the drive plate <b>971</b>, to allow continuous or otherwise automatically controlled feeding of slurry for systems employing a slurry with the polishing media. The present invention is not limited to use with the carrier described in <figref idref="DRAWINGS">FIG. 14</figref>, but may be used with more conventional carriers, including those that employ a substrate backing pad, and those that rotate. Other designs, such as those with bladder-filled, conformable crowns and other pressure arrangements for conforming the crown of a carrier, may also be used.

0085In the embodiment of <figref idref="DRAWINGS">FIG. 14</figref>, flow through the rings <b>961</b>, <b>962</b> and <b>963</b> may be set to deliver an equal flow rate/pressure of air/liquid, or a constant pressure profile or both may coincide. Additionally, the outermost ring <b>961</b> can be formed very close to the edge of the faceplate <b>955</b> to enable the pressure wave to extend at a substantially constant value nearly to the edge of the faceplate. The bearing layer <b>970</b> further enables the substrate to “float” or precess with respect to the faceplate <b>955</b>, since the faceplate <b>955</b> does not contact the backside of the substrate once the layer <b>970</b> has been formed. The radius of the substrate <b>260</b> is somewhat smaller than that of the faceplate, and the substrate is maintained in position between the faceplate <b>955</b> and the polishing media <b>310</b> by the presence of containment ring <b>868</b>.

0086The combination of the ability to apply substantially uniform load pressure over the entire surface of the backside of the substrate with the ability to allow the substrate to precess or float within the confines of the containment ring results in a very uniform polishing process that removes material consistently from the edge of the substrate to the center.

0087Alternatively, in situations where shaping or conformation of the pressure profile is required, the flow through the rings <b>961</b>, <b>962</b> and <b>963</b> can be varied to achieve the desired conformation of the pressure profile.

0088During polishing with the arrangement of <figref idref="DRAWINGS">FIG. 14</figref>, in addition to the application of force by applicators <b>960</b> by the carrier as described above, the vacuum applied through <b>890</b> to the polishing media and within the carrier <b>860</b>, draws the polishing media <b>310</b> against the substrate <b>260</b>, and is held in position there by the force of atmospheric pressure P_apressing against the polishing media <b>310</b> on the back side thereof with uniform pressure, while the back surface of the substrate <b>260</b> is supported by fluid/air pressure supplied by the carrier <b>860</b>, or by vacuuming the substrate to the carrier through a full porous sheet, for example.

0089Advantageously, this arrangement requires no vertical force application of the carrier <b>860</b> against the support <b>856</b>. Thus, the drive plate <b>971</b> only needs to provide horizontal force during polishing. Nor is a precision polishing surface required, since the actual polishing action is accomplished out of contact with the support <b>856</b>, with the polishing media <b>310</b> being pressed against the polishing surface of the substrate <b>260</b>. This greatly reduces the required weight of the polish processing machine as well as reducing the cost of the support <b>856</b>. Additionally, since the support <b>856</b> may be made much less bulky and less heavy, this enable multiple units or modules to be stacked much more easily, for parallel processing of substrates. Such modules may be stacked or oriented with the polishing surface of the wafer in a horizontal configuration facing up, in a horizontal configuration facing down, or in a vertical or other “off-horizontal” configuration.

0090Another optional feature of the carrier <b>860</b> is the provision of a faceplate <b>955</b> which is formed out of a transparent material, such as polycarbonate with an electrostatic film on the surface thereof, for example. The provision of a transparent faceplate <b>955</b> allows an observer to confirm that the substrate is properly precessing during polishing.

0091<figref idref="DRAWINGS">FIG. 15</figref> is a sectional view of another preferred embodiment of a substrate carrier <b>1060</b> which uses vacuum both for control of the substrate extension by the carrier plate, as well as to supply a fixation force for holding the substrate against the carrier. In this arrangement, the carrier plate <b>1155</b> is mounted to a carrier loading column <b>1110</b>, via seal plate <b>1120</b> and carrier plate down stop <b>1172</b> extending from containment ring support <b>1170</b>. A diaphragm <b>1140</b> is mounted between the seal plate <b>1120</b> and the carrier plate <b>1155</b> to form a pressurizable chamber <b>1145</b>.

0092The location of the carrier loading column <b>1110</b> forms the basis for gross positioning of the carrier. The location of the carrier loading column <b>1110</b> provides the primary load control of the containment ring <b>1180</b> which provides side load bearing control of the substrate during polishing.

0093A vacuum source <b>1130</b> is connected to a second pressurizable chamber <b>1134</b> via main vacuum lines <b>1132</b>, which are connected to vacuum holes <b>1147</b> in the containment ring support <b>1170</b>. Vacuum wafer pick up holes <b>1182</b> in the carrier plate <b>1155</b> are connected to an independently controllable vacuum/pressure source (not shown) via manifold <b>1184</b> which is joined to at least one vacuum port <b>1166</b> by vacuum tubing and fixtures (not shown). The application of vacuum through vacuum holes <b>1182</b> fixes the back side of a substrate against the carrier plate <b>1155</b>. In this example, four rings of vacuum holes are provided in addition to a vacuum hole centrally located through the face <b>1155</b>′ of carrier plate <b>1155</b>, although other configurations of vacuum holes could be alternatively used. Additionally, monitoring holes <b>1192</b> may be provided intermediate the vacuum hole <b>1182</b> arrangements to be used for monitoring the pressure and/or flow at the locations of their placement. The monitoring holes may be independently connected to individual monitoring pressure/flow sensors (not shown) or may be connected to a central sensing unit (not shown) though manifold <b>1194</b>.

0094A differential vacuum line <b>1160</b> connects with pressurizable chamber <b>1145</b> and an orifice <b>1162</b> is provided at an opposite end of vacuum line <b>1160</b> which is exposed to atmospheric pressure. A valve <b>1164</b>, preferably a bleed valve, interconnects the main vacuum line <b>1132</b> and the differential vacuum line <b>1160</b>. The valve <b>1164</b> may be adjusted so as to close off the differential vacuum line <b>1160</b> to the vacuum source <b>1130</b>, in which case the pressurizable chamber <b>1145</b> will assume atmospheric pressure via the orifice <b>1162</b>. This relatively high pressure expands the pressurizable chamber to drive the diaphragm <b>1148</b> and thus the carrier plate <b>1155</b> and face <b>1155</b>′ downward in <figref idref="DRAWINGS">FIG. 15</figref>, which effectively provides a greater polishing force on the substrate. Carrier plate down stop <b>1172</b> prevents overextension of the carrier face <b>1155</b>′ in the downward direction by limiting the downward movement of the carrier plate <b>1155</b>.

0095The valve <b>1164</b> may be adjusted so as to open the differential vacuum line <b>1160</b> to the vacuum source <b>1130</b> and to variably adjust the amount of flow, in which case the pressurizable chamber <b>1145</b> will assume pressure values less than atmospheric pressure. This contracts the pressurizable chamber to draw the diaphragm <b>1148</b> and thus the carrier plate <b>1155</b> upward in <figref idref="DRAWINGS">FIG. 15</figref>, which effectively provides a lesser polishing force on the substrate. The degree of upward movement is controllable by varying the flow through adjustments of the valve <b>1164</b> as referred to above.

0096During polishing with this arrangement, similar to the arrangement of <figref idref="DRAWINGS">FIG. 14</figref>, vacuum is also applied to the polishing media to draw the polishing media <b>310</b> against the substrate <b>260</b>, and the polishing media is held in position by the force of atmospheric pressure P_apressing against the polishing media <b>310</b> on the back side thereof with uniform pressure, while the back surface of the substrate <b>260</b> is held by the vacuum applied through the carrier faceplate <b>1155</b>′, as described above.

0097Similar advantages to those discussed with regard to the embodiment in <figref idref="DRAWINGS">FIG. 14</figref> also exist with regard to this embodiment. In order to control the generation of heat that ensues from the abrasion of the substrate and the frictional forces between the substrate and the polishing media, misters or air sprayers may be used to apply one or more flows of cooling streams against the backside of the polishing media <b>310</b>, i.e., the side which does not directly contact the substrate. Alternatively, a water bed may be provided in contact with the backside of the polishing media <b>310</b>.

0098It may also be desirable to provide a more rigid backing on the polishing media <b>310</b> by vacuuming a thin polycarbonate sheet (e.g., about 0.060 inches thick) to the backside of the media. Alternatively, stiffness could be increased by simply increasing the thickness of the polishing media itself. Additionally or alternatively, the backing sheet may be slit with grooves on the side which contacts the back side of the polishing media to enhance uniformity and planarization of the substrate.

EXAMPLES

00991. A polishing support surface is provided with a substantially rectangular sealing barrier having dimensions of about 22″×19″. A single vacuum port is provided centrally and at one end of the polishing surface defined within the perimeter of the sealing barrier. By applying a vacuum pressure of about 2 psig, the approximately 418 in²provides approximately 836 pounds of attractive force to a polishing media that overlies the support surface and which makes a vacuum seal with the sealing barrier. This extra load eliminates stretch, migration and buckling of the polishing media, and may be used to eliminate the need for tensioning of the polishing media. The polishing media is a MYLAR™ film having a fixed abrasive on the polishing area thereof, and is supplied by 3M Company or DuPont.

01002. In addition to the same conditions as in (1) above, an IC1000 layer is positioned as a subpad beneath the polishing media and above the support surface. When the vacuum is applied through the vacuum port, the polishing area of the polishing media is drawn down against the subpad and the support surface. Air is depleted from the spaces between the polishing media, subpad and support surface, causing a compression of the subpad and also causing the portions of the polishing media overlying the pores of the subpad to be partially drawn into the pores. As a mixture of KOH and water is supplied to the polishing surface of the polishing media, the polishing operation is commenced. Movement of the wafer carrier, wafer retaining ring and the wafer against the polishing media tends to sweep out the KOH/water polishing solution from the polishing area.

0101However, dimples in the polishing media, which were formed by the portions of the polishing media overlying the pores of the subpad being partially drawn into the pores of the subpad by the vacuum, trap small pools of the KOH/water polishing fluid thereby making the polishing fluid continuously available to the wafer surface being polished.